linux-kernel - Re: [PATCH V2 3/3] gpio: tegra: Add support for gpio debounce

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Message-ID: <571658CE.1040306@wwwdotorg.org>
Date:	Tue, 19 Apr 2016 10:11:58 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Laxman Dewangan <ldewangan@...dia.com>
Cc:	linus.walleij@...aro.org, gnurou@...il.com,
	thierry.reding@...il.com, linux-gpio@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 3/3] gpio: tegra: Add support for gpio debounce

On 04/19/2016 03:43 AM, Laxman Dewangan wrote:
> NVIDIA's Tegra210 support the HW debounce in the GPIO
> controller for all its GPIO pins.
>
> Add support for setting debounce timing by implementing the
> set_debounce callback of gpiochip.

> diff --git a/drivers/gpio/gpio-tegra.c b/drivers/gpio/gpio-tegra.c

> @@ -327,6 +360,9 @@ static int tegra_gpio_resume(struct device *dev)
>   			tegra_gpio_writel(bank->oe[p], GPIO_OE(gpio));
>   			tegra_gpio_writel(bank->int_lvl[p], GPIO_INT_LVL(gpio));
>   			tegra_gpio_writel(bank->int_enb[p], GPIO_INT_ENB(gpio));
> +			tegra_gpio_writel(bank->dbc_cnt[p], GPIO_DBC_CNT(gpio));
> +			tegra_gpio_writel(bank->dbc_enb[p],
> +					  GPIO_MSK_DBC_EN(gpio));

Why not just write to the "regular" register rather than the mask 
register here...

> @@ -351,6 +387,10 @@ static int tegra_gpio_suspend(struct device *dev)
>   			bank->oe[p] = tegra_gpio_readl(GPIO_OE(gpio));
>   			bank->int_enb[p] = tegra_gpio_readl(GPIO_INT_ENB(gpio));
>   			bank->int_lvl[p] = tegra_gpio_readl(GPIO_INT_LVL(gpio));
> +			bank->dbc_enb[p] = tegra_gpio_readl(
> +							GPIO_MSK_DBC_EN(gpio));
> +			bank->dbc_enb[p] = (bank->dbc_enb[p] << 8) ||
> +						bank->dbc_enb[p];

... since that would avoid having to or in the mask value in the saved 
register value here; you could just save/restore the regular register in 
the same way as any other register.